diff --git a/packages/datadog-api-client-v1/models/ObjectSerializer.ts b/packages/datadog-api-client-v1/models/ObjectSerializer.ts
index e5d375b7657f..997512e3b7af 100644
--- a/packages/datadog-api-client-v1/models/ObjectSerializer.ts
+++ b/packages/datadog-api-client-v1/models/ObjectSerializer.ts
@@ -3339,31 +3339,52 @@ export class ObjectSerializer {
 
       const instance = new typeMap[type]();
       const attributesMap = typeMap[type].getAttributeTypeMap();
-      const attributesBaseNames = Object.keys(attributesMap).reduce(
-        (o, key) => Object.assign(o, { [attributesMap[key].baseName]: "" }),
-        {}
-      );
+      const keepAllInAdditional =
+        (typeMap[type] as any)._keepTypedInAdditionalProperties === true;
+      // Single pass: build attributesBaseNames (for extra-key detection) and, when needed,
+      // baseNameToAttr (for per-field typed deserialization preserving int64 precision).
+      const attributesBaseNames: { [key: string]: string } = {};
+      const baseNameToAttr: { [key: string]: any } = {};
+      for (const attrName in attributesMap) {
+        const baseName = attributesMap[attrName].baseName;
+        attributesBaseNames[baseName] = "";
+        if (keepAllInAdditional && attrName !== "additionalProperties") {
+          baseNameToAttr[baseName] = attributesMap[attrName];
+        }
+      }
       const extraAttributes = Object.keys(data).filter(
-        (key) => !Object.prototype.hasOwnProperty.call(attributesBaseNames, key)
+        (key) =>
+          keepAllInAdditional ||
+          !Object.prototype.hasOwnProperty.call(attributesBaseNames, key)
       );
 
       if (extraAttributes.length > 0) {
         if ("additionalProperties" in attributesMap) {
-          if (!instance.additionalProperties) {
-            instance.additionalProperties = {};
-          }
-
           const additionalProperties: { [key: string]: any } = {};
-          for (const key of extraAttributes) {
-            additionalProperties[key] = data[key];
+          if (keepAllInAdditional) {
+            for (const key of extraAttributes) {
+              const attrInfo = baseNameToAttr[key];
+              // Use per-field type/format for typed attrs to preserve int64 precision.
+              additionalProperties[key] = attrInfo
+                ? ObjectSerializer.deserialize(
+                    data[key],
+                    attrInfo.type,
+                    attrInfo.format
+                  )
+                : data[key];
+            }
+            instance.additionalProperties = additionalProperties;
+          } else {
+            for (const key of extraAttributes) {
+              additionalProperties[key] = data[key];
+            }
+            const attributeObj = attributesMap["additionalProperties"];
+            instance.additionalProperties = ObjectSerializer.deserialize(
+              additionalProperties,
+              attributeObj.type,
+              attributeObj.format
+            );
           }
-
-          const attributeObj = attributesMap["additionalProperties"];
-          instance.additionalProperties = ObjectSerializer.deserialize(
-            additionalProperties,
-            attributeObj.type,
-            attributeObj.format
-          );
         } else {
           throw new Error(
             `found extra attributes '${extraAttributes}' in ${type}`
diff --git a/packages/datadog-api-client-v1/models/UsageSummaryDate.ts b/packages/datadog-api-client-v1/models/UsageSummaryDate.ts
index dc74ed981206..9f9bba0933c3 100644
--- a/packages/datadog-api-client-v1/models/UsageSummaryDate.ts
+++ b/packages/datadog-api-client-v1/models/UsageSummaryDate.ts
@@ -1269,6 +1269,11 @@ export class UsageSummaryDate {
    */
   "_unparsed"?: boolean;
 
+  /**
+   * @ignore
+   */
+  static readonly _keepTypedInAdditionalProperties = true;
+
   /**
    * @ignore
    */
diff --git a/packages/datadog-api-client-v1/models/UsageSummaryDateOrg.ts b/packages/datadog-api-client-v1/models/UsageSummaryDateOrg.ts
index 2180f8b16ba4..5bd804d09d3e 100644
--- a/packages/datadog-api-client-v1/models/UsageSummaryDateOrg.ts
+++ b/packages/datadog-api-client-v1/models/UsageSummaryDateOrg.ts
@@ -1292,6 +1292,11 @@ export class UsageSummaryDateOrg {
    */
   "_unparsed"?: boolean;
 
+  /**
+   * @ignore
+   */
+  static readonly _keepTypedInAdditionalProperties = true;
+
   /**
    * @ignore
    */
diff --git a/packages/datadog-api-client-v1/models/UsageSummaryResponse.ts b/packages/datadog-api-client-v1/models/UsageSummaryResponse.ts
index 0aff482a5798..45180af90e89 100644
--- a/packages/datadog-api-client-v1/models/UsageSummaryResponse.ts
+++ b/packages/datadog-api-client-v1/models/UsageSummaryResponse.ts
@@ -1315,6 +1315,11 @@ export class UsageSummaryResponse {
    */
   "_unparsed"?: boolean;
 
+  /**
+   * @ignore
+   */
+  static readonly _keepTypedInAdditionalProperties = true;
+
   /**
    * @ignore
    */
diff --git a/packages/datadog-api-client-v2/models/ObjectSerializer.ts b/packages/datadog-api-client-v2/models/ObjectSerializer.ts
index f435551d4819..7a7939949d3f 100644
--- a/packages/datadog-api-client-v2/models/ObjectSerializer.ts
+++ b/packages/datadog-api-client-v2/models/ObjectSerializer.ts
@@ -14701,31 +14701,52 @@ export class ObjectSerializer {
 
       const instance = new typeMap[type]();
       const attributesMap = typeMap[type].getAttributeTypeMap();
-      const attributesBaseNames = Object.keys(attributesMap).reduce(
-        (o, key) => Object.assign(o, { [attributesMap[key].baseName]: "" }),
-        {}
-      );
+      const keepAllInAdditional =
+        (typeMap[type] as any)._keepTypedInAdditionalProperties === true;
+      // Single pass: build attributesBaseNames (for extra-key detection) and, when needed,
+      // baseNameToAttr (for per-field typed deserialization preserving int64 precision).
+      const attributesBaseNames: { [key: string]: string } = {};
+      const baseNameToAttr: { [key: string]: any } = {};
+      for (const attrName in attributesMap) {
+        const baseName = attributesMap[attrName].baseName;
+        attributesBaseNames[baseName] = "";
+        if (keepAllInAdditional && attrName !== "additionalProperties") {
+          baseNameToAttr[baseName] = attributesMap[attrName];
+        }
+      }
       const extraAttributes = Object.keys(data).filter(
-        (key) => !Object.prototype.hasOwnProperty.call(attributesBaseNames, key)
+        (key) =>
+          keepAllInAdditional ||
+          !Object.prototype.hasOwnProperty.call(attributesBaseNames, key)
       );
 
       if (extraAttributes.length > 0) {
         if ("additionalProperties" in attributesMap) {
-          if (!instance.additionalProperties) {
-            instance.additionalProperties = {};
-          }
-
           const additionalProperties: { [key: string]: any } = {};
-          for (const key of extraAttributes) {
-            additionalProperties[key] = data[key];
+          if (keepAllInAdditional) {
+            for (const key of extraAttributes) {
+              const attrInfo = baseNameToAttr[key];
+              // Use per-field type/format for typed attrs to preserve int64 precision.
+              additionalProperties[key] = attrInfo
+                ? ObjectSerializer.deserialize(
+                    data[key],
+                    attrInfo.type,
+                    attrInfo.format
+                  )
+                : data[key];
+            }
+            instance.additionalProperties = additionalProperties;
+          } else {
+            for (const key of extraAttributes) {
+              additionalProperties[key] = data[key];
+            }
+            const attributeObj = attributesMap["additionalProperties"];
+            instance.additionalProperties = ObjectSerializer.deserialize(
+              additionalProperties,
+              attributeObj.type,
+              attributeObj.format
+            );
           }
-
-          const attributeObj = attributesMap["additionalProperties"];
-          instance.additionalProperties = ObjectSerializer.deserialize(
-            additionalProperties,
-            attributeObj.type,
-            attributeObj.format
-          );
         } else {
           throw new Error(
             `found extra attributes '${extraAttributes}' in ${type}`